A colloidal AgI sol is made by mixing 32 mL of 0.018 M KI with 20 mL of 0.015 M AgNO3. Assuming complete precipitation of AgI, find the concentration of unreacted I^- in the mixture in mM, to two decimals.

JEE Advanced levelNumerical answerDifficulty 3 of 3sc164

A colloidal AgI sol is made by mixing $32 mL$ of $0.018 M$ $KI$ with $20 mL$ of $0.015 M$ $AgNO X_{3}$ . Assuming complete precipitation of AgI, find the concentration of unreacted $I X^{-}$ in the mixture in mM, to two decimals.

Numerical answer type, answer in mM, tolerance 0.02.

Moles of

I X^{-}

32 \times 0.018 = 0.576

mmol and of

Ag X^{+}

20 \times 0.015 = 0.300

mmol. Excess

I X^{-}

0.276

mmol, which makes the sol negative. Total volume = 52 mL, so concentration =

0.276/52 = 5.31

mM.